Cooling system in a vehicle

ABSTRACT

A cooling system with a circulating coolant for cooling a combustion engine in a vehicle ( 1 ) includes a first radiator ( 13 ), a first line circuit ( 14, 15, 16 ) which leads coolant from the first radiator ( 13 ) to the engine ( 2 ); a second line circuit ( 17, 18 ) which leads coolant from the engine ( 2 ) to the first radiator ( 13 ); a second radiator ( 20 ) upstream of the first radiator ( 13 ) in air flow through radiators; a third line circuit ( 21, 22, 24 ) including at least one line ( 21, 24 ) to lead coolant from a line ( 16 ) in the first line circuit to the second radiator ( 20 ), and a fourth line circuit ( 25, 26   a - d,    27 ) which leads coolant from the second radiator ( 20 ) to the first line circuit ( 15 ) and which contains at least one cooler ( 29, 30, 31 ) for cooling a medium or component of the vehicle ( 1 ).

BACKGROUND TO THE INVENTION AND PRIOR ART

The present invention relates to a cooling system in a vehicle according to the preamble of claim 1.

There are quite a number of coolers and components in a vehicle which need cooling to a lower temperature than can be achieved with the coolant in the combustion engine's cooling system. One such cooler is the condenser in an AC system. The condenser is usually situated at the front portion of the vehicle in front of the radiator where it is cooled by air at the temperature of the surroundings. However, it is not possible for all of the coolers and components which need cooling to a low temperature to be situated in front of the vehicle's radiator in contact with air at the temperature of the surroundings. Examples of coolers and components which it is also desirable to cool with a colder medium than the coolant are oil coolers for gearbox oil, oil coolers for servo oil, brake compressors, turbines and electrical control units.

The coolant in the engine's cooling system is in many cases used also to cool other media and components than the combustion engine. Certain media or components which the cooling system cools may require a very high momentary cooling effect. One example of such a component is a hydraulic retarder. If the cooling system is used to cool the hydraulic oil of a hydraulic retarder, it needs to deliver a very large cooling effect when the retarder is activated. If the retarder is used to brake a vehicle on a long downgrade, the load upon the cooling system may be of long duration, with consequent risk of overheating the coolant in the cooling system.

The amount of air which can be supplied to a supercharged combustion engine depends on the pressure of the air but also on the temperature of the air. Supplying the largest possible amount of air to the engine entails the compressed air being cooled in a charge air cooler before it is led to the engine. The compressed air is usually cooled in a charge air cooler situated at a front portion of a vehicle. This makes it possible for the compressed air to be cooled to a temperature substantially corresponding to that of the surroundings. In cold weather conditions, the compressed air is cooled in the charge air cooler to a temperature which may be below the dewpoint temperature of the air, resulting in precipitation of water vapour in liquid form in the charge air cooler. When the temperature of the surrounding air is lower than 0° C., there is also risk that the precipitated water might freeze to ice within the charge air cooler. Such ice formation would cause a greater or lesser amount of obstruction of the air flow ducts within the charge air cooler, resulting in a reduced flow of air to the engine and consequent operational malfunctions or stoppages.

The technique known as EGR (exhaust gas recirculation) is a known way of recirculating part of the exhaust gases from a combustion process in a combustion engine. The recirculating exhaust gases are mixed with the inlet air to the engine before the mixture is led to the engine. Adding exhaust gases to the air causes a lower combustion temperature resulting inter alia in a reduced content of nitrogen oxides NO_(x) in the exhaust gases. This technique is used both for Otto engines and for diesel engines. The recirculating exhaust gases are cooled in at least one EGR cooler before being mixed with the inlet air. A known practice is to use EGR coolers in which the recirculating exhaust gases are cooled to a temperature substantially corresponding to that of the surroundings. Exhaust gases contain water vapour which condenses within the EGR cooler when they are cooled to a temperature below the dewpoint of the water vapour. If the temperature of the surrounding air is below 0° C., there is also risk that the condensed water might freeze to ice within the EGR cooler. Such ice formation would cause a greater or lesser amount of obstruction of the exhaust gas flow ducts within the EGR cooler, causing the nitrogen oxides content of the exhaust gases to increase.

SUMMARY OF THE INVENTION

The object of the present invention is to propose a cooling system in a vehicle which makes it possible to cool a large number of components of the vehicle to a low temperature. Another object of the cooling system is that it be capable of coping with momentary peak loads. A further object of the cooling system is that it be capable of preventing ice formation in coolers which contain water vapour.

The first of these objects is achieved with the cooling system of the kind mentioned in the introduction which is characterised by the features indicated in the characterising part of claim 1. In the portion of the cooling system herein referred to as the first line circuit the coolant will be at a relatively low temperature after it has been cooled in the radiator. In the portion of the cooling system herein referred to as the second line circuit, the coolant will be at a relatively high temperature after it has cooled the engine. The cooling system according to the present invention comprises an extra line loop. The extra line loop contains a second radiator situated at a location upstream of the ordinary radiator and a third line circuit by which it is possible to lead relative cold coolant from the first line circuit to the second radiator. The first radiator and the second radiator are with advantage fitted in a region situated at a front portion of the vehicle. The second radiator is here situated at least partly in front of the first radiator. A cooler fan and the draught caused by forward movement of the vehicle provide here an air flow in a direction such that it passes through the second radiator before passing through the first radiator.

In this case, relatively cold coolant is thus taken from the first line circuit and led to a second radiator in which it undergoes a further step of cooling by air which is at a lower temperature than the air which cools the coolant in the first radiator. The coolant thus undergoes cooling in the second radiator to a low temperature which in favourable circumstances may be close to that of the surroundings. The cold coolant leaving the second radiator is led to a fourth line circuit in which it cools at least one medium or component in a coolant-cooled cooler. The cold coolant in the fourth line circuit is used with advantage to cool media or components which require cooling to a low temperature. In this case the various media or components need not have a cooler situated at a front portion of the vehicle.

According to a preferred embodiment of the present invention, the fourth line circuit comprises at least two parallel lines each provided with its respective cooler to cool a respective medium or component of the vehicle. The cold coolant in the fourth line circuit is used with advantage to cool two or more media or components which require cooling to a low temperature. Having the cold coolant pass through a number of parallel lines each provided with its respective cooler makes it possible for all of the media to be cooled by coolant at the same low temperature. It is possible, however, for one or more coolers to be arranged in series with one another in the fourth line circuit.

According to another preferred embodiment of the present invention, the third line circuit comprises at least one line by which it is possible lead coolant from the second line circuit to the second radiator. In this case, warm coolant is thus led to the second radiator. This may be appropriate at times when there is heavy load upon the cooling system. In this case, warm coolant is thus cooled in both the first radiator and the second radiator. The capacity of the cooling system may thus be increased to cope with momentary peak loads. The third line circuit comprises with advantage a valve means which in a first position directs coolant from a line in the first line circuit to the second radiator and in a second position directs coolant from a line in the second line circuit to the second radiator. With such a valve means, which may be a three-way valve, relatively cold coolant or warm coolant may be directed alternately to the second radiator.

According to another preferred embodiment of the present invention, the cooling system comprises a control unit adapted to receiving information from a sensor which monitors a parameter related to the coolant temperature in the cooling system. Said sensor monitors with advantage the temperature of the coolant in the second line circuit where it has its highest temperature. The control unit may be a computer unit or the like provided with suitable software for the purpose. The control unit can put the valve means into the second position when it receives information from said sensor that the coolant is at a higher temperature than a reference value. When the coolant temperature rises above a reference value which may be a highest acceptable coolant temperature, the control unit in this case automatically leads warm coolant also to the second radiator. When the coolant temperature falls below a reference value, the control unit can put the valve means back into the first position when the extra cooling of the coolant is no longer needed. The cooling system may comprise a cooler to cool a medium or component in the second line circuit. In this case the already warm coolant which has cooled the engine is thus used to cool a further medium or component of the vehicle. This component may be an oil cooler for hydraulic oil used in a hydraulic retarder. At times when the vehicle is being braked by a hydraulic retarder, the cooling system will be subject to a large momentary load. At times when the retarder is activated, the control unit may immediately put the valve means into the second position so that warm coolant goes to the second radiator to increase the capacity of the cooling system

According to another preferred embodiment, the second radiator is situated at a location upstream of a cooler for cooling a gaseous medium which contains water vapour. The gaseous medium which is led to the engine may be charge air or recirculating exhaust gases. Most diesel engines and many petrol engines are supercharged, i.e. they have a turbo unit which draws in and compresses surrounding air which is led to the engine. The compressed air therefore contains water vapour in an amount which varies with the moisture content of the surrounding air. As the compressed air has a higher dewpoint than air at the pressure of the surroundings, water may condense in the charge air cooler. The compressed air should therefore not be cooled to a temperature below 0° C., since this might result in condensed water vapour freezing to ice within the charge air cooler. The engine's exhaust gases also contain water vapour in an amount which varies with the moisture content of the surrounding air. Recirculating exhaust gases are also at a higher pressure than surrounding air. In many cases it is therefore difficult to prevent water vapour from condensing within an air-cooled EGR cooler. The recirculating exhaust gases should therefore not be cooled to a temperature below 0° C., since this might result in condensed water vapour in the EGR cooler freezing to ice.

According to another preferred embodiment, the cooling system comprises a control unit adapted to receiving information from a sensor which monitors a parameter related to whether there is ice formation or risk of ice formation in the cooler, and to putting the valve means into the second position when it receives information from said sensor which indicates that there is ice formation or risk of ice formation in the cooler. Said sensor may be a temperature sensor which monitors the temperature of the medium when it leaves the cooler. If the medium is at a lower temperature than 0° C., ice is likely to form within the cooler. When the control unit receives such information, it will put the valve means into the second position so that warm coolant is led to the second radiator. Air flowing through the second radiator will thus acquire a raised temperature. When this warm air reaches the downstream cooler, it will melt any ice which has formed within the cooler. When the control unit receives information from said sensor that there is no longer risk of ice formation, it will put the valve means back into the first position.

According to another embodiment of the invention, the fourth line circuit comprises a bypass line and a valve by which the coolant can be directed past the line with said cooler. Warm coolant will thus be led through the second radiator at times when there is heavy load upon the cooling system and when there is ice formation in a cooler in the form of a charge air cooler or EGR cooler. In such situations it is also of advantage to increase the coolant flow through the second radiator. A bypass line makes it possible for the coolant to be led past the coolers in the fourth line circuit. The pressure drop in the fourth line circuit is thus reduced, thereby increasing the flow of coolant through the second radiator and the capacity of the cooling system.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below by way of example with reference to the attached drawings, in which:

FIG. 1 depicts a cooling system according to a first embodiment of the present invention and

FIG. 2 depicts a cooling system according to a second embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 depicts a vehicle 1 powered by a supercharged combustion engine 2. The vehicle 1 may be a heavy vehicle powered by a supercharged diesel engine. The exhaust gases from the cylinders of the engine 2 are led via an exhaust manifold 3 to an exhaust line 4. The exhaust gases in the exhaust line 4, which will be at above atmospheric pressure, are led to a turbine 5 of a turbo unit. The turbine 5 is thus provided with driving power which is transferred, via a connection, to a compressor 6. The compressor 6 thereupon compresses the air which is led into an inlet line 8 via an air filter 7. A charge air cooler 9 is provided in the inlet line 8. The charge air cooler 9 is situated in a region A at a front portion of the vehicle 1. The purpose of the charge air cooler 9 is to cool the compressed air before it is led to the engine 2. The compressed air is cooled in the charge air cooler 9 by air which is forced through it by a cooler fan 10 and the draught caused by forward movement of the vehicle. The cooler fan 10 is driven by the engine 2 via a suitable connection.

The engine 2 is cooled by coolant which circulates in a cooling system. The coolant is circulated in the cooling system by a coolant pump 11. The cooling system comprises also a thermostat 12. The coolant in the cooling system is intended to be cooled in a first radiator 13 fitted at a forward portion of the vehicle 1 in the region A. The first radiator 13 is situated downstream of the charge air cooler 9 with respect to the direction of cooling air flow in the region A. The cooling system comprises a first line circuit in the form of lines 14, 15, 16 which lead the coolant from the first radiator 13 to the engine 2. The coolant pump 11 is situated in the line 16. The cooling system comprises a second line circuit in the form of lines 17, 18 which lead the coolant from the engine 2 to the first radiator 13. The line 17 comprises a retarder cooler 19 to cool hydraulic oil used in a retarder. At times when the coolant is at too low a temperature, the thermostat 12 leads it from the line 17 to the engine 2 via the lines 15, 16. In that situation the coolant is thus not cooled in the first radiator 13.

The cooling system comprises an extra line loop. The extra line loop comprises a third line circuit which leads coolant to a second radiator 20. The third line circuit comprises a line 21 connected to the line 16 of the first line circuit, and a line 22 connected to the line 17 of the second line circuit. The third line circuit comprises a three-way valve 23. When the three-way valve 23 is in a first position, it directs the relatively cold coolant from the line 21 and the line 24 to the second radiator 20. When the three-way valve 23 is in a second position, it directs the warm coolant from the line 22 and the line 24 to the second radiator 20. The second radiator 20 is situated at the front portion of the vehicle 1 at a location upstream of the first radiator 13 and upstream of the charge air cooler 9 with respect to the direction of cooling air flow in the region A. The extra line loop comprises also a fourth line circuit which leads cold coolant from the second radiator 20 to the line 15 in the first line circuit. The fourth line circuit comprises an initially common line 25. The common line 25 splits into four parallel lines 26 a-d. The four parallel lines 26 a-d join together to form a common line 27 which leads the coolant to the line 15 in the first line circuit.

The first parallel line takes the form of a bypass line 26 a provided with a valve 28 by which the flow through the bypass line 26 a can be regulated. The second parallel line 26 b contains a cooler in the form of a condenser 29 in an AC system of the vehicle 1. The coolant cools a circulating refrigerant in the condenser 29 to a temperature at which it condenses. The third parallel line 26 c contains a cooler 30 to cool servo oil of the vehicle 1. The fourth parallel line 26 d contains a cooler 31 to cool servo oil of the vehicle 1. All of these media need cooling to a low temperature. The cooling system comprises a control unit 32 to control the three-way valve 23 and the valve 28. The control unit 32 receives information from a first temperature sensor 33 which monitors the temperature of the coolant in the line 17 at a location downstream of the retarder cooler 19, and a second temperature sensor 34 which monitors the temperature of the charge air in the inlet line 8 after it has been cooled in the charge air cooler 9.

During operation of the vehicle, the coolant pump 11 circulates coolant in the cooling system. The control unit 32 substantially continuously receives information from the temperature sensor 33 about the temperature of the coolant in the line 17 and [about the temperature of the charge air when it leaves the charge air cooler 9. At times when the coolant is at an acceptable temperature below a reference value and the charge air is at an acceptable temperature above a reference value, the control unit 32 keeps the three-way valve in the first position. When the three-way valve 23 is in the first position, the coolant pump 11 leads part of the coolant in the line 16 to the engine 2.

This portion of the coolant is subsequently led through the retarder cooler 19 and the lines 17 and 18 to the first radiator 13. A remaining portion of the coolant is led by the coolant pump 11 to the second radiator 20 via the line 21, the three-way valve 23 and the line 24. This portion of the coolant is cooled in the second radiator 20 by air at the temperature of the surroundings. The coolant leaving the second radiator 20 may thus be at a temperature close to that of the surroundings. The cold coolant is led from the second radiator 20 to the line 25. In this situation the control unit keeps the valve 28 in a closed position. The cold coolant from the line 25 will thus be led in parallel through the three lines 26 b-d in which it cools the refrigerant in the condenser 29, the gearbox oil in the cooler 30 and the servo oil in the cooler 31. These media undergo very good cooling by the cold coolant. The coolant from the parallel lines 26 b-d comes together in the line 27 which leads it to the line 15 and the coolant pump 11.

If the control unit 32 receives information that the temperature of the coolant has risen above the reference value, a larger capacity of the cooling system is required. The coolant temperature rising about the reference value may be due to the vehicle being braked by the hydraulic retarder. The cooling system is under heavy load when the coolant has also to cool the air in the retarder cooler 19. In this situation, the control unit 32 puts the three-way valve 23 into the second position whereby part of the warm coolant in the line 17 will be led to the second radiator 20 via the line 22, the three-way valve 23 and the line 24. In this situation, warm coolant is thus cooled both in the first radiator 13 and in the second radiator 20. This results in a greater temperature difference between the coolant and the air in the second radiator 20. The capacity of the cooling system to cool the coolant increases. To further increase it, the control unit 32 may open the valve 28 so that the cold coolant leaving the second radiator 20 is mainly led through the bypass line 26 a. This reduces the flow resistance for the cold coolant in the extra line loop. The coolant flow through the second line circuit 20 increases, resulting in a further increase in the capacity of the cooling system. When it receives information that the temperature of the coolant has fallen to an acceptable level below a reference value, the control unit 32 closes the valve 28 and puts the three-way valve 23 into the first position.

If it receives information from the temperature sensor 34 that the charge air is at a lower temperature than 0° C., the control unit 32 will find that ice is forming in the charge air cooler. It will then put the three-way valve 23 into the second position. Part of the warm coolant in the line 17 will thus be led to the second radiator 20 via the line 22, the three-way valve 23 and the line 24. The air flowing through the second radiator 20 will thus undergo a marked temperature rise by the warm coolant before it reaches the downstream charge air cooler 9. The air reaching the charge air cooler 9 will thus be at a definitely higher temperature than 0° C. Any ice which has formed within the charge air cooler 9 will therefore melt. To further increase the cooling system's defrosting capacity, the control unit 32 may open the valve 28 so that cold coolant leaving the second radiator 20 is mainly led through the bypass line 26 a. This decreases the flow resistance for the cold coolant through the extra loop. The flow of warm coolant through the second radiator 20 will increase, resulting in still better de-icing of the charge air cooler 9. When it receives information that the temperature of the charge air has risen back to an acceptable level, the control unit 32 will put the valve 28 into the closed position and the three-way valve 23 into the first position.

FIG. 2 depicts an alternative cooling system. In this case the combustion engine 2 is equipped with an EGR (exhaust gas recirculation) system to recirculate the exhaust gases. A return line 35 for recirculation of exhaust gases here extends from the exhaust line 4 to the inlet line 8. The return line 35 contains an EGR valve 36 by which the exhaust flow in the return line 35 can be shut off. The EGR valve 36 may also be used to steplessly control the amount of exhaust gases led from the exhaust line 4 to the inlet line 8 via the return line 35. The return line 35 comprises an EGR cooler 37 to cool the exhaust gases before they are mixed with the charge air in the inlet line 8 and are led to the engine 2. In this case the control unit 32 receives also information from a temperature sensor 38 which monitors the temperature of the recirculating exhaust gases after they have been cooled in the EGR cooler 37.

During operation of the engine 2, the control unit 32 receives information from the temperature sensor 38 about the temperature of the recirculating exhaust gases after they have been cooled in the second EGR cooler 37. The control unit 32 compares the temperature values received with a reference temperature. Preventing ice formation in the second EGR cooler 37 may involve using a reference temperature of 0° C. As soon as it receives information from the first temperature sensor 38 that the recirculating exhaust gases are above the reference temperature, the control unit 32 will put the valve means into the first position. If it receives information from the temperature 38 that the recirculating exhaust gases have been cooled to below the reference temperature, the control unit 32 will put the valve means 23 into the second position. Part of the warm coolant in the line 17 will thus be led to the second radiator 20 via the line 22, the three-way valve 23 and the line 24. The air flowing through the second radiator 20 undergoes a marked temperature increase before it reaches the downstream EGR cooler 37. The air reaching the EGR cooler 37 will thus be at a definitely higher temperature than 0° C. Any ice which has formed within the EGR cooler 37 will therefore melt. When it receives information that the temperature of the recirculating exhaust gases has risen back to an acceptable level, the control unit 32 will put the three-way valve 23 into the first position.

In other respects, this embodiment has the same characteristics as in FIG. 1 except that it has no bypass line 26 a. When the three-way valve 23 is in the first position, there will thus here again be good cooling of the coolant in the second radiator 20. The cold coolant from the second radiator is used to cool refrigerant in the condenser 29, gearbox oil in the cooler 30 and servo oil in the cooler 31. At times when the coolant is at too high a temperature, the three-way valve 23 may be put into the second position so that warm coolant is led through the second radiator 20 with the object of increasing the capacity of the cooling system. At times when the charge air leaving the charge air cooler 9 is at too low a temperature, the three-way valve 23 will likewise be put into the second position. In this situation warm coolant is led through the second radiator 20 with the object of de-icing the downstream charge air cooler 9.

The invention is in no way restricted to the embodiments described but may be varied freely within the scopes of the claims. 

1. A cooling system with a circulating coolant for cooling a combustion engine in a vehicle, the system comprises: a first radiator in which the coolant is cooled by an air flow in a direction through the first radiator; a first line circuit which leads coolant from the first radiator to the engine, a second line circuit which leads coolant from the engine to the first radiator; a second radiator at a location upstream of the first radiator with respect to the direction of the air flow so that at least part of the air flow through the second radiator flows also through the first radiator; a third line circuit which comprises at least a first coolant line which leads coolant from a line in the first line circuit to the second radiator; the third line circuit comprises at least a second coolant line which leads coolant from a line in the second line circuit to the second radiator; the third line circuit includes a valve device operable to a first position for leading coolant from the line in the first line circuit to the second radiator, and operable to a second position for leading coolant from the line in the second line circuit to the second radiator; and a fourth line circuit which leads coolant from the second radiator to the first line circuit and the fourth line circuit contains at least one cooler for cooling a medium or component of the vehicle.
 2. A cooling system according to claim 1, wherein the fourth line circuit comprises at least two parallel lines each including a cooler configured and located for cooling a respective medium or component of the vehicle.
 3. A cooling system according to claim 1, further comprising: a sensor configured for monitoring a parameter related to the coolant temperature in the cooling system; and a control unit configured for receiving information from the sensor for controlling an aspect of the system based on the information.
 4. A cooling system according to claim 3, wherein the aspect of the system is the valve device and the control unit is configured for putting the valve device into the second position when the control unit receives information from the sensor that the coolant is at a higher temperature than a reference value.
 5. A cooling system according to claim 1, further comprising a cooler for cooling a medium or component in the second line circuit.
 6. A cooling system according to claim 1, wherein the second radiator is at a location in the vehicle and the location is, with respect to the direction of the air flow through the radiator, upstream of a cooler for cooling a gaseous medium, wherein the medium contains water vapour, so that at least part of the air which flows through the second radiator flows also through said coolers.
 7. A cooling system according to claim 6, further comprising: a sensor which monitors a parameter related to whether there is ice formation or risk of ice formation in the coolers; and a control unit configured for receiving information from the sensor, and for putting the valve device into the second position when the control unit receives information from the sensor that there is ice formation or risk of ice formation in the coolers.
 8. A cooling system according to claim 2, wherein the fourth line circuit comprises a bypass line and a second valve by which the coolant is led through the bypass line and thus past the lines with the coolers. 